This invention relates to a workpiece folding device for a sewing machine which can form a fold along the peripheral edge of a workpiece.
As a method for forming a fold along the peripheral edge of a workpiece, Japan Published Unexamined Utility Model Application No. 63-91275 is proposed by the same applicant as that of the present invention. As shown in FIG. 5A, a pocket cloth P is placed on a gage plate 24, a press plate 28 covers the gage plate 24 together with the pocket cloth P, and the peripheral edge of the pocket cloth P is bent down along the contour of the gage plate 24. Subsequently, as shown in FIG. 5B, a plurality of folding pieces 35 supported on a folding-pieces support member 32 are moved from the side of the gage plate 24 to the underside of the gage plate 24 by air cylinders 33. The peripheral edge of the pocket cloth P is thus folded. In this prior-art device, the distance T between the gage plate 24 and each of the folding pieces 35, both of which are positioned above a table 14, is adjusted before the folding operation.
However, the prior-art device has problems when the distance T between the gage plate 24 and each of the folding pieces 35 is considerably short or long.
When the distance T is too long, the folding pieces 35 are positioned below the folding-pieces support member 32. After the pocket cloth P is folded at its periphery, the gage plate 24, the folding pieces 35 and the pocket cloth P are pressed onto the table 14 all together. Then, so large load is applied to the folding pieces 35 that the folding pieces 35 may be deformed or broken. After that, when the folding pieces 35 are detached from the gage plate 24, the folded edge of the pocket cloth P may be bulged out of the gage plate 4. Thus, it is difficult for the prior-art device to form a beautiful fold.
When the distance T is too short, the folding pieces 35 may push up the peripheral edge of the gage plate 24 or bump the gage plate 24 via the pocket cloth P, thus hurting the gage plate 24. Further, during the withdrawal of the folding pieces 35, folded peripheral edge of the pocket cloth P may be pulled out of the gage plate 24 due to the frictional force between the pocket cloth P and the folding pieces 35.
In addition, it is time-consuming and tedious operation to adjust a plurality of the folding pieces 35 in a way that the distance T between the gage plate 24 and each of the folding pieces 35 are uniform.